1. Field of the Invention
The present invention relates to a semiconductor device with a data line arrangement for preventing a noise interference, and in particular to an improved semiconductor device with a data line arrangement for preventing a noise interference which is capable of decreasing or eliminating a noise interference among data lines of a high-integrated memory device.
2. Description of the Background Art
A digital system with a high performance and fast operation is increasingly needed. In order to implement such digital system, a high-integrated memory is generally used. The integrity of the memory device has been increased in combination with an improved memory cell structure and fabrication method. However, as the integrity is increased, a noise interference in a memory device is increased. Namely, when the integrity of the memory device is increased, the distances between data lines is decreased, and a coupling capacitance between data lines is also increased thereby. Therefore, the noise interference is increased.
FIG. 1 is a schematic view illustrating a semiconductor device which is implemented by combining a folded data line and a vdd/2 precharge technique. As shown therein, the data lines DB0, /DB0, DB1, and /DB1 which are regularly spaced-apart are horizontally arranged, and a sense amplifier SAi (i=1,2, . . . ) is connected to one end of each pair of data lines DBi, /DBi (i=1,2, . . . ). The pair of data lines DBi, /DBi and a word line WL0 are intersected each other, and a memory cell M is connected at an intersected portion between the data line and the word line.
As shown in FIG. 1, in the regularly spaced-apart data lines, assuming that the signal at the data line DB0 is -Vs, the signal voltage of Vdd/2 is detected at the data line /DB0 based on the Vdd/2 precharge method. A noise of -.delta.1 is generated at the data line /DB0 based on the coupling capacitance between the data lines DB0 and /DB0. In addition, when a signal voltage at the data line DB1 neighboring with the data line /DB0 becomes -Vs, the noise of -.delta.1 is generated based on the coupling capacitance between the data lines /DB0 and DB1. As a result, the signal at the data line /DB0 becomes Vdd/2-2.delta.1, and the signal voltage difference with respect to the data line DB0 is decreased. The thusly decreased signal voltage is inputted into the sense amplifier, and a signal which is different from the signal read from a memory cell may be outputted. Therefore, it is impossible to correctly read the data from the memory cell. A method is disclosed, which is capable of decreasing a noise interference by balancing the coupling capacitance between the data lines.
FIG. 2 is a schematic view illustrating the structure for decreasing a noise interference between the data lines (or bit lines).
Four pairs of the data lines DBi, /DBi(i=1,2,3,4) are shown therein. Each data line consists of the data lines DBi and /DBi. Each pair of the data lines consisting of the data lines DBi and /DBi is connected with the sense amplifier SAi. Namely, the data lines DB0 and /DB0 are connected with the sense amplifier SA0, and the data lines DB1 and /DB1 are connected with the sense amplifier SA1, and the data lines DB2 and /DB2 are connected with the sense amplifier SA2, and the data lines DB3 and /DB3 are connected with the sense amplifier SA3. Each sense amplifier SAi is connected at the ends of the data lines DBi and /DBi. The sense amplifiers SAi and SA(i+1) are connected at the opposed end of the data lines. In addition, the word lines WLi(i=0,1, . . . ) are insulatively intersected by the four pairs of the data lines. The memory cells M are provided at the intersected portion between the word lines WLi (in the drawings, only two word lines WL0 and WL1 are shown) and the data lines DBi and /DBi. In addition, the data lines DB0 and /DB0 are twisted at an intermediate position of the data lines in the longitudinal direction. In addition, the data lines DB2 and /DB2 are twisted at an intermediate position of the data lines in the longitudinal direction. Here, the twisted portion of the data lines DB0 and /DB0 is called as a twisted crossing section T1. The twisted portions of the data lines DB1 and /DB1 are called as twisted crossing sections T2 and T3. The data lines DB1 and /DB1 forms twisted crossing sections T2 and T3 at the 1/4 position and 3/4 position in the longitudinal direction. The twisted crossing section T1 of the neighboring data lines DB0 and /DB0 is formed at an intermediate position between the twisted crossing sections T2 and T3 of the data lines DB1 and /DB1. In addition, the solid line shown in FIG. 2 represents a first layer wiring and the dotted line represents a second layer wiring. Namely, the solid line and dotted line represent the layers which are different from each other.
The structure of the twisted data line arrangement has the following advantages. The data line DB0 among the twisted data lines generates a noise interference due to the coupling capacitances of the neighboring data lines DB1 and /DB1 and the data line /DB0. The data line /DB0 generates a noise interference due to the coupling capacitance of the data lines DB0, DB1 and /DB1. Therefore, in the signal voltage outputted from the sense amplifier positioned at the end portions of the data lines DB0 and /DB0, the noise interference is offset, so that it is possible to stably read the data. In addition, in the neighboring data lines DB1 and /DB1, since the noise interference is identical based on the coupling capacitance at each data line, the noise interference which affects the signal voltage of the data line is eliminated. Namely, the data line DB1 among the data lines forms a coupling capacitance in combination with the neighboring data lines DB0 and /DB0. The data line /DB1 generates the noise interference based on the coupling capacitance in combination with the neighboring data lines DB0 and /DB0 and the data line DB1 which forms a pair with the data line /DB1. Therefore, since each data line pair receives the identical noise interference from the neighboring data lines, it is possible to prevent the data reading error.
FIG. 3 is a plan view illustrating the pattern of a semiconductor device of FIG. 2.
The data lines DB0, /DB0, DB1, /DB1, DB2, /DB2, DB3, /DB3 (namely, hatched portions) are horizontally arranged on a semiconductor substrate 1 using an insulation film (not shown). The uppermost line is called as a first line, and the line lower than the first line is called as a second line, and the line lower than the second line is called as a third line. Namely, the lines are sequentially given its corresponding number down to the eighth line. The dotted portion in FIG. 3 represents a wiring line or by-pass line for connecting the data lines. The wiring line may be formed in a lower layer of the data line or in an upper layer thereof. Assuming that the data line is a first conductive layer formed on the upper surface of the semiconductor substrate 1, and the connection wiring line is formed therebelow, the connection wiring line may be formed using a diffusion layer having a conductivity by implanting a dopant into the semiconductor substrate 1. Namely, the diffusion layer 2 is formed on the surface of the semiconductor substrate 1, and an insulation layer is formed on the upper surface of the semiconductor substrate 1. The data lines DB0 and /DB0, which are the first conductive layer, are arranged on the upper surface of the insulation layer. At this time, the data line DB0 among the data lines is formed of a first conductive layer and is longitudinally extended. The data line DB0 is horizontally extended from the first line and is downwardly curved at the intermediate portion, and then is horizontally extended toward the second line. The data line /DB0 is broken or separated at the portion in which the diffusion layer 2 is formed. The data line /DB0 formed on the left side of the diffusion layer is horizontally arranged with respect to the second line, and the data line /DB0 formed in the right side of the diffusion layer is formed at the first line, and the data line /DB0 formed spacedly from the first and second lines is connected with the diffusion layer 2 through contact holes 2a and 2b. Namely, the twisted crossing section of the data line is implemented on the semiconductor substrate using a diffusion layer. The insulation layer (not shown) is formed on the data lines DB0, . . . , /DB3 formed as the first conductive layer instead of the diffusion layer 2. In addition, the second conductive layer is formed as a wiring line arranged on the insulation layer (not shown) at the portion of the diffusion layer, so that the separated lines are connected for thereby implementing a twisted data line. If the data lines DB0, . . . , /DB3 are formed as a second layer wiring line among the multilayer wiring lines formed on the semiconductor substrate, the connection wiring line for forming the twisted crossing section may be implemented using the first layer wiring line arranged below the second layer wiring line or the third layer wiring line arranged on the second layer wiring line.
The twisted crossing section T1 of the data lines DB0 and /DB0 is formed at the intermediate portion of the twisted crossing sections T2 and T3 of the neighboring data lines DB1 and /DB1.
As described above, a method is disclosed, which is capable of eliminating a noise interference by balancing the coupling capacitance between the neighboring data lines. However, in the conventional art, the data lines are formed on the identical plane, and the connection wiring line is formed on a layer which is different from the data lines.
Namely, since the data lines are formed on the identical plane, the occupying area of the data lines is increased in the semiconductor device. Therefore, it is difficult to increase the integrity of the semiconductor device.